1. Field of the Invention
The present invention relates to an illuminating system for an image processing measuring apparatus used for measuring dimension, shape or contour and the like of an object based on an image of the object which has been measured by means of an optical system. More specifically, the invention relates to an illuminating system for an image processing measuring apparatus wherein illumination to be applied to an object is adapted to be capable of selecting from a group consisting of vertical-incident illumination, inclined-incident illumination, and ring-shaped incident illumination.
2. Prior Art
In an image processing measuring apparatus wherein a site measured in an object is optically magnified by means of a magnifying optical system, whereby dimension, shape or contour and the like of the object are measured from the magnified image, for example, measuring microscope, tool maker's microscope, projector or the like, illumination with respect to the object to be measured has a very important function from the viewpoint of attaining a clear magnified image of such object. Heretofore, a vertical-incident illuminating system wherein illuminating light is projected upon an object from the direction substantially directly above the object has been known as an illuminating system in such type of the image processing measuring apparatus as described above. However, such vertical-incident illuminating systems are utilized in most cases where an object having a comparatively simple shape is measured, so that if an object having a complicated contour such as a step-shaped object having a number of edge sections, is measured, a shadow of such edge sections cannot be clearly displayed on a display unit or the like.
In this respect, to solve the above described disadvantage, there has been proposed an image processing measuring apparatus wherein an inclined-incident illuminating device having a separate light source from that typically used in the image processing measuring apparatus, or a ring-shaped incident illuminating device having similarly a separate light source from that of the measuring apparatus is mounted on the measuring apparatus main body, and an image of the object measured is obtained by illumination derived from these illuminating devices.
In the above-mentioned inclined-incident illuminating device or ring-shaped incident illuminating device, however, since a separate light source from that involved in an image processing measuring apparatus is required, it becomes expensive, and labor intensive because it is difficult to mount the light sources to the measuring apparatus main body in a prescribed posture. Furthermore, in such an arrangement that an inclined-incident illuminating device and a ring-shaped incident illuminating device were mounted to the measuring apparatus main body at the time of initially assembling the whole apparatus, the apparatus itself becomes large in size and difficult to operate because all the illuminating devices are not always required necessarily dependent upon applications of the image processing measuring apparatus.